论文标题
超出参数放大的标准量子极限
Beyond the standard quantum limit of parametric amplification
论文作者
论文摘要
弱微波信号的低噪声放大对于量子信息处理中无数方案至关重要。量子力学将最终的下限设置为一半光子的最终下限，以添加输入噪声，以进行窄带信号的相位扩增，也称为标准量子极限（SQL）。该限制相当于最大量子效率为$ 0.5 $，可以通过采用非排定参数放大的宽带信号来克服。我们表明，原则上可以达到最大量子效率1。在实验上，我们发现通过使用通量驱动的Josephson参数放大器和宽带热信号，我们发现$ 0.69 \ pm 0.02 $，远远超出了SQL。我们预计我们的结果可以在检测超大微波信号的检测方面进行基本改进。
The low-noise amplification of weak microwave signals is crucial for countless protocols in quantum information processing. Quantum mechanics sets an ultimate lower limit of half a photon to the added input noise for phase-preserving amplification of narrowband signals, also known as the standard quantum limit (SQL). This limit, which is equivalent to a maximum quantum efficiency of $0.5$, can be overcome by employing nondegenerate parametric amplification of broadband signals. We show that, in principle, a maximum quantum efficiency of 1 can be reached. Experimentally, we find a quantum efficiency of $0.69 \pm 0.02$, well beyond the SQL, by employing a flux-driven Josephson parametric amplifier and broadband thermal signals. We expect that our results allow for fundamental improvements in the detection of ultraweak microwave signals.
